.\" Generated from openpam_subst.c by gendoc.pl
.Dd May 31, 2025
.Dt OPENPAM_SUBST 3
.Os
.Sh NAME
.Nm openpam_subst
.Nd substitute PAM item values in a string
.Sh SYNOPSIS
.In sys/types.h
.In security/pam_appl.h
.In security/openpam.h
.Ft "int"
.Fn openpam_subst "const pam_handle_t *pamh" "char *buf" "size_t *bufsize" "const char *template"
.Sh DESCRIPTION
The
.Fn openpam_subst
function expands a string, substituting PAM item
values for all occurrences of specific substitution codes.
The
.Fa template
argument points to the initial string.
The result is stored in the buffer pointed to by the
.Fa buf
argument; the
.Fa bufsize
argument specifies the size of that buffer.
The actual size of the resulting string, including the terminating NUL
character, is stored in the location pointed to by the
.Fa bufsize
argument.
.Pp
If
.Fa buf
is NULL, or if the buffer is too small to hold the expanded
string,
.Fa bufsize
is updated to reflect the amount of space required to
hold the entire string, and
.Fn openpam_subst
returns
.Dv PAM_TRY_AGAIN .
.Pp
If
.Fn openpam_subst
fails for any other reason, the
.Fa bufsize
argument is
untouched, but part of the buffer may still have been overwritten.
.Pp
Substitution codes are introduced by a percent character and correspond
to PAM items:
.Bl -tag -width 18n
.It \&%H
Replaced by the current value of the
.Dv PAM_RHOST
item.
.It \&%h
Replaced by the current value of the
.Dv PAM_HOST
item.
.It \&%s
Replaced by the current value of the
.Dv PAM_SERVICE
item.
.It \&%t
Replaced by the current value of the
.Dv PAM_TTY
item.
.It \&%U
Replaced by the current value of the
.Dv PAM_RUSER
item.
.It \&%u
Replaced by the current value of the
.Dv PAM_USER
item.
.El
.Sh RETURN VALUES
The
.Fn openpam_subst
function returns one of the following values:
.Bl -tag -width 18n
.It Bq Er PAM_SUCCESS
Success.
.It Bq Er PAM_BAD_ITEM
Unrecognized or restricted item.
.It Bq Er PAM_TRY_AGAIN
Try again.
.El
.Sh SEE ALSO
.Xr pam 3 ,
.Xr pam_get_authtok 3 ,
.Xr pam_get_item 3 ,
.Xr pam_get_user 3 ,
.Xr pam_strerror 3
.Sh STANDARDS
The
.Fn openpam_subst
function is an OpenPAM extension.
.Sh AUTHORS
The
.Fn openpam_subst
function and this manual page were
developed by
.An Dag-Erling Sm\(/orgrav Aq Mt des@des.dev .
